Tomorrow, Marvel's The Avengers will open in certain parts of the globe—not the U.S., which won't see the film until May 4—and Marvel's four-year odyssey of laying the groundwork for this action blockbuster will finally be over. It's been an impressive run commercially, if not always critically. (Captain America: The First Avenger was just all right, and my guess is I'm fonder of the appealingly dopey Thor than you are.) Nonetheless, The Avengers (or Avengers Assemble, as it's known in some countries) is going to be a titanic hit—and, even better, it's actually really good.

Marvel should be really proud of its achievement. But I'm worried about what the post-Avengers landscape is going to look like—for Marvel and for everybody else who wants to make a big comic-book movie. Those kinds of summer extravaganzas aren't going away, certainly, but our expectations may be altered for a while. And not for the better.

I should say right off the bat that The Avengers isn't some masterpiece. (It's not The Dark Knight.) But it's very fun and very entertaining in a comic-book (as opposed to graphic-novel) sort of way. Still, The Avengers definitely feels like the culmination of something. It's become a tired joke by this point, but since 2008's Iron Man, we've been going to these Marvel movies knowing that we had to sit through all the credits for that oblique final scene that hinted at the assembling of the Avengers. Pretty quickly, it began to feel like a gimmick, reducing Iron Man, The Incredible Hulk, Iron Man 2, Thor, and Captain America to one long commercial for a future film that Marvel really, really hoped you'd want to see ...

And now that The Avengers is here ... well, now what? We've come all this way with these characters, and we've invested a lot of time (and, don't forget, money) on them. Where do we go from here? Once you've seen Iron Man pal around with all these other superheroes (not to mention Black Widow and That Bow-and-Arrow Guy Jeremy Renner Plays), are you going to be happy just watching a movie with Iron Man in it? Marvel sure hopes so: Iron Man 3 comes out a year from now. And there's going to be another Thor movie and another Captain America movie, too. No matter how you feel about the Star Wars franchise at this moment, imagine if George Lucas had decided every year to release one or two movies starring just one of its characters. Would you want to watch Princess Leia 2 or Chewbacca 3? That's precisely what's coming our way from Marvel in the next couple years.

But it's not just that we're going to have to make do with a bunch of separate Avengers movies until the inevitable Avengers 2. There's also the growing difficulty of grappling with all these different storylines. Jon Favreau, who directed the first two Iron Man movies, hit on this problem back when he was still considering directing Iron Man 3:

"In theory, 'Iron Man 3' is going to be a sequel or continuation of 'Thor,' 'Hulk,' 'Captain America' and 'Avengers,'" he said. "This whole [Marvel] world... I have no idea what it is. I don't think [the other directors] do either, from conversations I've had with those guys."

That's perhaps one of the reasons why he opted out of Iron Man 3. (Or maybe it was because he was reportedly annoyed that Marvel wanted to cram a lot of the other Avengers into it.) I could tolerate the individual Avenger movies when the other characters were mostly limited to the end credits, but if each one of the new movies will be a Where's Waldo? of unnecessary cameos, then we're getting dangerously close to a lot of flicks like Iron Man 2, which was half-movie, half-Avengers setup. The worst-case scenario is that Marvel manages to turn its cash cow into "The Simpsons Spin-Off Showcase."

But the problem extends to all the other comic-book movies heading our way, including the other ones Marvel is making. The Avengers isn't going to make people uninterested in seeing The Dark Knight Rises or The Amazing Spider-Man or Man of Steel. (For crying out loud, it's Batman and Spider-Man and Superman.) But after feasting on The Avengers and all its superheroes, is anyone going to care about a Green Lantern or even a Wolverine in quite the same way? Hey, I like Hugh Jackman, too, but he's just one action hero. How can he compare with Iron Man and the Hulk and everybody else in the same movie? I'm scared that The Avengers will convince filmmakers that they've got to double- and triple-up their comic-book characters to get audiences to come. Or even worse, we're going to have lame Batman Vs. Superman-like ideas. (Seriously, that almost happened before Christopher Nolan stepped in to do Batman Begins.)

It's the Hollywood equivalent of mission creep, and the certain success of The Avengers will just as certainly teach the studios all the wrong lessons. ("We need to make that Justice League flick ASAP!") I hope you enjoy The Avengers as much as I did. I just worry that we'll spend the next decade hating all the kitchen-sink comic-book movies it is sure to spawn.

Grierson & Leitch is a regular column about the movies. Follow us on Twitter, @griersonleitch. Top image by Jim Cooke.